Communications systems are typically modular in design, made of various communications modules that include hardware and software that transmit inter-module communications signals, such as data or clock signals, in order to support communications traffic running through the communications system. In such a communications system, several communications modules may connect to a chassis through which the modules send communications signals to one another. The chassis may include a backplane with a number of socket-type connectors, and the modules may include pin-type card connector(s). The card connector(s), if compatible with the chassis backplane connectors, mate with the backplane connectors, thereby connecting to the chassis backplane and completing a communications path to other modules.
Often, a communications system supports a number of different modules that connect to the backplane. However, a particular backplane connector may not be compatible with a particular module's card connector(s). If such a connection is made without regard to connector compatibility, an incorrect connection may result, possibly preventing desired communications or even damaging the system. Moreover, a module intended to connect to the correct backplane connector may be oriented incorrectly, causing an improper connection, no connection, or damage to the connectors. In these and other cases when incorrect connections may occur, it is preferable to prevent incorrect connections.